Characteristics of temporal patterns of cortisol and luteinizing hormone in primiparous,postpartum, anovular,suckled, beef cows exposed acutely to bulls

Background  

The physiological mechanism by which bulls stimulate resumption of ovarian cycling activity in postpartum, anovular, suckled cows after calving may involve the concurrent activation of the hypothalamic-hypophyseal-ovarian (HPO) axis and hypothalamic-hypophyseal-adrenal (HPA) axis. Thus, the objectives of this experiment were to determine if characteristics of temporal patterns of cortisol and luteinizing hormone (LH) in postpartum, anovular, beef cows are influenced by acute exposure to bulls. The null hypotheses were that daily, temporal characteristics of cortisol and LH concentration patterns do not differ between cows exposed acutely to bulls or steers.     

On the origins of esterases

Comparisons among the primary sequences of five cloned eukaryotic esterases reveal two distinct lineages, neither bearing any significant overall sequence similarity to the functionally related serine protease multigene family. We have not eliminated the possibility that the esterases may have residual conformational similarities to the serine proteases. However, our profile analysis and analyses of the predicted conformations of the esterases reveal little similarity to the serine proteases. Four of the esterase proteins share 27%-53% overall sequence similarity and evidence of a catalytic mechanism involving the same Arg- Asp-Ser or His-Asp-Ser charge relay. We propose that these four esterases, three of them cholinesterases, form part of a multigene family essentially separate from the serine proteases.